December, 2018: Having lost the House in the mid-terms, Trump reduces his demand to just $5.7 billion to build a smaller portion of his wall.

December, 2018: Having failed to get his $5.7 billion, Trump turns down a Democratic offer of $1.6 billion and refuses to sign the annual budget.

February, 2019: Having rejected the previous offer of $1.6 billion so forcefully that he was willing to shut down the government, Trump now signs a bill authorizing only $1.4 billion.

===

On January 19, 2018, Trump had negotiated the perfect deal. He would get $25 billion for his wall, in return for which he only had to offer a DACA deal that he had already agreed with in multiple tweets. He had persuaded the other side to agree to everything he wanted without giving up anything he opposed. He needed neither a shutdown nor a national emergency, just outstanding negotiations.

When objective historians write about the Trump era, the puzzle they will have to decipher is the sentence above in red. Why did he renege on what, from his point of view, was the perfect deal? Was it just the usual reason (co-President Hannity disliked the deal), or was there something more complicated?